1. Field of the Invention
The present invention is concerned with a portable load making and breaking tool especially adapted for use by utility linemen working in and around high voltage transmission and distribution equipment. More particularly, it is concerned with such a load making and breaking device which provides a reliable make and break function by virtue of vacuum-enclosed electrical contacts, and further includes secondary, series-connected contacts constructed such that the user can visually observe a large air gap between the secondary contacts when the latter are open.
2. Description of the Prior Art
During work and repair of electrical transmission and distribution lines, it is often very desirable to make and/or break electrical loads. That is to say, in many instances it is preferred to disconnect or connect a system under load, i.e., while current is passing therethrough. Load making and breaking allows work to be done on a portion of a distribution system, for example, with a minimium of unnecessary outages to unaffected customers. Additionally, such work can be performed under much safer working conditions when the load is properly broken.
Generally speaking, load breaking cannot be realistically accomplished simply through the use of mechanical switches and the like. This for the reason that attempts to break load currents in this fashion cause arcing between the switch contacts during the opening sequence, which in turn can damage such equipment. Thus, specialized devices have heretofore been provided for load breaking which serve to positively break the load without equipment damage.
In electrical distribution systems, a series of switches and/or cutout units are usually provided for sectionalizing the system. Cutouts are fused for circuit protection, and also can be opened manually should the need arise in order to open the section or sections of the circuit protected by the cutout. As noted above however, conventional cutout and/or switches cannot generally be used for circuit making and breaking under load. Thus, it has been the practice to make or break the load at an upstream position or the like having specialized equipment for this purpose; however, this is undesirable in that a large portion of the distribution system is affected, even though only a minor portion thereof needs attention. In order to overcome this problem, devices have been provided for attachment in parallel to cutouts or switches which serve to break a current load passing therethrough. One such device is commercialized under the designation "Loadbuster." In the use of such a device, the latter is placed in parallel with a cutout or switch, and the equipment is manually opened. At this point the load breaking device is actuated to break the current load without damage to the cutout or switch. The "Loadbuster" unit is deficient, however, inasmuch as it is incapable of making a load. Moreover, in order to be used, it must be mounted onto and in parallel with a cutout or other mechanical switchgear. Thus, it is useless in situations such as when a spur line is connected to a main transmission or distribution line simply by the use of a short stretch of interconnecting conductor and without any mechanical cutouts or switchgear interposed therein. Finally, the expulsion principle of operation of this unit makes it less than optimum from the standpoint of safety and reliability. Further, it cannot safely be used with rubber gloves alone; hot stick operation is required.
In short, there is a need for a portable load making and breaking device which has universal applicability in that it can be used in contexts wherein no mechanical connect-disconnect apparatus is employed.
In order for any load make or break device to be truly useful, it must not only be reliable in practice, but must be reasonably safe in operation. This in turn means that the device must be capable of quickly suppressing any arcing which may occur during load making and breaking operations. Furthermore, linemen and others concerned with safe practices have expressed a strong preference for devices of this character which give a positive visual assurance of a load break. As can be appreciated, any prudent linemen would be very hesitant to work around supposedly unenergized electrical equipment without first assuring himself that the circuit had indeed been opened.